Patent Application
20080277206
This invention generally relates to load bearing members for use in elevator systems. More particularly, this invention relates to load bearing members that include at least one tension member and an outer polymer jacket.
Elevator systems are widely known and used. Typical arrangements include an elevator cab that moves between landings in a building, for example, to transport passengers or cargo between different building levels. A motorized elevator machine moves a rope or belt assembly, which typically supports the weight of the cab, and moves the cab through a hoistway.
The elevator machine includes a machine shaft that is selectively rotationally driven by a motor. The machine shaft typically supports a sheave that rotates with the machine shaft. The ropes or belts are tracked through the sheave such that the elevator machine rotates the sheave in one direction to lower the cab and rotates the sheave in an opposite direction to raise the cab.
A rope or belt typically includes one or more tension members to support the weight of the elevator cab. These tension members may be encapsulated in a polymer jacket. One type of tension member comprises steel strands with a polymer jacket. The jacket surrounds the tension members and provides traction between the rope or belt and the sheave.
Conventional jacket application processes leave portions of the cords uncovered by the jacket material. One known technique includes depositing a zinc coating on the steel tension members to protect the exposed portions from corrosion that may result from exposure to the environment in a hoistway.
One disadvantage of typical jacketed ropes and belts may be insufficient adhesion between the polymer jacket and the tension members. The adhesion provides a “pull-out” strength to maintain a desired alignment of the tension members and the jacket. The adhesion also is responsible for transferring the weight of the elevator cab from the jacket to the steel cords. If the weight is not effectively transferred from the weaker jacket material to the stronger steel material, the jacket may be subjected to overstressing. The use of a zinc coating on the steel as mentioned above may further impair a desired level of adhesion.
Another disadvantage of typical ropes and belts may be frictional wear between the steel strands. As the rope or belt bends over a sheave, for example, the steel strands of a tension member may slide relative to each other and rub together. Repeated sliding may subject the steel strands to undesirable wear over a period of time. Conventional zinc coatings do little to reduce this problem.
There is a need for a rope or belt assembly that has improved adhesion between the tension members and the jacket. This invention addresses that need and provides enhanced capabilities while avoiding the shortcomings and drawbacks of the prior art.
An exemplary load bearing member useful in an elevator system includes at least one elongated tension member, and a conversion coating on the elongated tension member. Some examples include a polymer jacket at least partially surrounding the elongated tension member. In one example, the conversion coating includes at least one of an oxide, a phosphate, or a chromate.
An example method of making a load bearing member includes coating at least one elongated tension member with a conversion coating. One example method includes at least partially surrounding the coated tension member with a polymer jacket. One example includes chemically bonding the conversion coating to the elongated tension member and mechanically bonding the conversion coating to the polymer jacket.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiments. The drawings that accompany the detailed description can be briefly described as follows.
In the example shown, the tension member 36 includes a plurality of strands 38, such as steel strands. Groups of strands 38 are bundled together to form cords 40. In the illustrated example, the tension member 36 includes one cord 40.
The circular cross-sections of the strands 38 result in space 41 between the strands 38. In the illustrated example, the material of the polymer jacket 34 at least partially penetrates and fills some of the space 41 during an extrusion or other process used to form the polymer jacket 34, for example.
In one example, the conversion coating 46 includes a phosphate coating having a selected amount of the chemical element manganese. In one example, the manganese provides an advantageous crystallographic structure for mechanical interlocking with the polymer jacket 34, as will be discussed below. In another example, the conversion coating 46 includes a phosphate coating having at least one of zinc, nickel, or chrome, or iron to provide an advantageous crystallographic structure.
In another example, the conversion coating 46 includes at least one of a chromium coating (hexavalent or trivalent) or a black iron oxide coating to provide an advantageous crystallographic structure with additional corrosion inhibition.
In one example, the conversion coating 46 is sealed by a known technique to fill at least a portion of any pores in the conversion coating 46. In another example, the conversion coating 46 is left unsealed.
In one example, the conversion coating 46 inhibits corrosion of the strand 38, promotes adhesion between the strand 38 and the polymer jacket 34, and provides lubricity between strands 38 that are wound together to form the cord 40.
In another example, the conversion coating 46 includes forming a phosphate coating using a known conversion coating technique such as chemical immersion, chemical spraying, or another process. The example phosphate includes the chemical element phosphorous bonded to oxygen, which forms an oxide. An active substance such as phosphoric acid reacts with the outer surface 44 of the strand 38 to form phosphorous oxide. The resulting phosphate coating is at least partially chemically bonded to the outer surface portion 44 and passivates the outer surface 44 to inhibit corrosion of the strand 38.
In the illustrated example, the phosphate coating provides lubricity and wear resistance between the strands 38 of a cord 40. The strands 38 may slide relative to each other in use when the load bearing member 24 wraps around the sheave 21 of a cord 40. For example, phosphate is known to be a solid lubricant and allows the strands 38 to slide against each other with less friction compared to previously used zinc-coated strands. Chemically bonding the phosphate coating to the outer surface 44 of the strand 38 provides the benefit of preventing the phosphate coating from easily delaminating, as may otherwise occur with a coating that is not chemically bonded. If a portion of a coating delaminates, the delaminated particle may act as an abrasive particle and accelerate wear between strands, for example.
In the example shown, the phosphate conversion coating 46 has an irregularly-shaped external surface 48. The irregularly-shaped surface 48 results from the crystallographic structure of the conversion coating 46. Such a surface facilitates mechanically locking the polymer jacket 34 to the tension member 36 to form a strong bond. The chemical bonding between the conversion coating 46 and the strands 38 along with the mechanical locking between the conversion coating 46 and the polymer jacket 34 provide the benefit of strong adhesion between the polymer jacket 34 and the tension member 36.
In one example, strong adhesion promotes efficient transfer of the weight of the elevator cab 12 from the polymer jacket 34 to the cords 40 and strands 38 of the tension member 36, as the jacket 34 is under compression between the tension member 36 and the sheave 21.
The strong adhesion also provides latitude in selecting the type of polymer for the polymer jacket 34. In one example, the polymer jacket 34 includes either a polyurethane variation or a different type of polymer than polyurethane. Without the conversion coating 46, the jacket material had to have selected properties to achieve sufficient bonding between the jacket 34 and the tension member 36. This limited the choices for jacket materials. With the superior adhesion provided by the conversion coating 46, a wider variety of materials are suitable candidates for forming the jacket. Another benefit associated with more freedom in choosing a jacket material is that the choice may be dictated, at least in part, by a desire to facilitate better molding when forming the jacket. Given this description, those skilled in the art will be able to select appropriate coating components and jacket materials to meet the needs of their particular situation.
In the example shown in
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2005/041408 | 11/14/2005 | WO | 00 | 4/15/2008 |
